This invention relates generally to plastic face shields which are pivotally mounted on various types of hard hats, such as fire fighters helmets, and which are worn in high temperature environments such as often encountered in burning buildings and the like. More specifically, the invention relates to means for preventing plastic material located in end sections of the shield near the pivotal attachment points from deforming and sagging below the hat brim when the shield is in a raised storage position and when exposed to high temperatures so as to prevent contact of the hot, sagging plastic with the wearer's face, neck and/or shoulders and thus prevent serious burns.
Fire helmets which have transparent plastic face shields pivotally attached thereto have long been known and used in the prior art. Typically, such prior art face shields are constructed of high temperature plastics such as polycarbonates, polysulfones, polyarylates and the like. While these face shield materials are usable in relatively high temperature environments of the type often encountered by fire fighters, they sometimes begin to melt under high temperature conditions such that the plastic material begins to deform, as by sagging or drooping.
During the initial stages of fire fighting activity, the wearer of such a helmet will often be clothed in high temperature protective apparel including, of course, a suitable protective face mask. Under those conditions, the plastic face shield is not used and is disposed in a raised storage position wherein a front portion of the face shield overlies the top of the helmet. Only after the initially intense flames are brought under manageable control and the situation becomes reasonably stabilized, does the chopping away of charred and smoldering timber, and the like usually begin wherein axes are used. When this latter is activity is about to commence, the fire fighter will tilt this face shield downwardly from its stored position into a face shielding position so as to protect his face against projectiles such as wood splinters, glass and so forth which are likely to be encountered when using an ax.
But during the initial stages of fire fighting activity where the heat encountered is likely to be at its most intense, the shield will normally be in the raised storage position and it is this stage with which my invention is principally concerned. Under such circumstances, prior art face shields in the stored position sometimes begin to sag and droop in the region of the diagonally extending lower margins of the end sections. Occasionally, such deformities are so severe that the plastic material of the end sections actually sags below the rim of the helmet where it can come into contact with the fire fighters face, neck and/or shoulders or into contact with his protective apparel. In either case, a serious burn, damage to his protective apparel or both, can occur.
Recently, the National Fire Protection Association has developed new standards for such plastic face shields which require these devices to withstand a temperature of 500.degree. for a five minute period without deforming to the extent of sagging or drooping below the brim of the helmet when in the stored position. The plastics commonly in use in face shields at this time, such as those previously mentioned, cannot, by themselves, meet such a standard.
By means of my invention, this difficulty is now overcome.